This tends to surprise most, as people tend to assume that tonality is a very complex feature - and that complex features are probably older, right? The reverse is true. The creation of tone changes was a labor saving device that made clear communication possible in less time.
Excitingly, a linguist of Mandarin has taken a sentence and mapped its evolution in pronunciation, starting with Old Chinese of 1200 BCE and progressing step-wise with each sound change till the modern era. Take a listen: